<!DOCTYPE html>
<html>
<head lang="en">
  <meta charset="UTF-8">
  <title></title>
  <link rel="stylesheet" href="http://cdn.bootcss.com/bootstrap/3.3.0/css/bootstrap.min.css">
  <link rel="stylesheet" href="style.css"/>
  <script src="http://cdn.bootcss.com/jquery/1.11.1/jquery.min.js"></script>
  <script src="http://cdn.bootcss.com/bootstrap/3.3.0/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container">
  <ul class="list-inline drop-down">
    <li class="drop-menu">
      <a>css</a>
      <div class="drop-content hidden">
        <ul>
          <li><a>css01</a></li>
          <li><a>css02</a></li>
          <li><a>css03</a></li>
        </ul>
      </div>
    </li>
    <li class="drop-menu"><a>html</a></li>
    <li class="drop-menu">
      <a>js</a>
      <div class="drop-content hidden">
        <ul>
          <li><a>js01</a></li>
          <li><a>js02</a></li>
        </ul>
      </div>
    </li>
  </ul>
</div>
<script>
 /**$(".drop-down").on("mouseover","li",function(){
    $(this).find(".drop-content").removeClass("hidden");
  });
  $(".drop-down").on("mouseout","li",function(){
    $(this).find(".drop-content").addClass("hidden");
  });**/
  function DropMenu(opt){
      this.hidden = "hidden";
     if(typeof opt == "object"){
         this.config(opt);
     }
  }
    DropMenu.prototype.config = function(opt){
        this.settings = $.extend({
            menuSelector : "",
            contentSelector: "",
            onOverOut : true
        },opt);
        if(this.settings.onOverOut){
            var _self = this;
            $(this.settings.menuSelector).on("mouseover","li",function(){
                $(this).find(_self.settings.contentSelector).removeClass(_self.hidden);
            });
            $(this.settings.menuSelector).on("mouseout","li",function(){
                $(this).find(_self.settings.contentSelector).addClass(_self.hidden);
            });
        }
    }
  new DropMenu({
      menuSelector : ".drop-down",
      contentSelector: ".drop-content"
  });
</script>
</body>
</html>